Nonsense ! - It´s just the requests of certain users which want more high ISO values. High ISO values tend to bring more noise with it and that has to be removed. Noise removing leads to a loss in sharpnes and details and this loss has to be compensated for. So the images must be resharpened. In other words : you get more flat regions without texture (texture cancelled by NR) and sharpend outlines of these regions. The result is some kind of water color or "waxy" appearance of your digital photographs.